Just wondering what would be the best way to make the molded-in rod holder on my 2010 outback larger so the rod holder extension tube will fit completely flush. It won't go completely down as the tube diameter is too small. It could go another 2" or so down. I tested multiple rod holder extensions and it is definitely the tube diameter on the kayak.

Any suggestions? Is it safe to sand down the inside of the rod holder? Or, should I sand down the extension tube and use only that one in that molded-in hole?